Polyvinyl alcohol (PVOH) is a commodity polymer that is used in a wide variety of different applications. However, PVOH is generally regarded as non-thermoplastic. PVOH has a high melting point of about 200.degree. C. depending on the degree of hydrolysis. As PVOH is heated near its melting point, yellowing and discoloration occur. Therefore, when using PVOH as a base material for thermoplastic applications, the PVOH must usually be modified.
Modified PVOH is used in many different water-dispersible thermoformable articles, such as fibers, films and fabrics which maintain their integrity and strength when in use, but dissolve and disperse when placed in contact with water. Unmodified PVOH is used in industry for many different solution-based applications and is not generally considered to be thermoformable or melt-processable. Some such applications for unmodified PVOH include warp sizing in textiles, fabric finishing, adhesives, paper processing additives, and emulsifiers/dispersants.
The prior art has demonstrated some success in modifying PVOH for use in thermoplastic applications. By "modified" PVOH, it is meant PVOH resin which has been chemically modified, including PVOH having another compound grafted thereto, or PVOH resin which has been mixed with one or more plasticizers. In each instance, these "modifications" have been needed to permit PVOH to be used in thermoformable articles.
To overcome the thermoplastic processing problems, chemically modified PVOH has been used. Some prior art teachings have used ethers of PVOH, ethoxylated PVOH or lacton-modified PVOH to produce thermoformable articles.
The prior art has also used PVOH that has not been modified structurally by adding a plasticizing agent to the PVOH which permits the PVOH to be extruded into films and fibers. Examples of plasticizers include water, ethylene glycol, glycerin and ethanolamine.
However, there are problems associated with the addition of plasticizers to PVOH. One of the most pronounced problems during processing is the fogging of the volatile plasticizer during the melt extrusion and condensing of vapor and effects of the vapor to the operating environment. In addition, the extruded articles such as films or fibers lose the plasticizers since the plasticizer molecules diffuse out of the film or fibers. This causes the films or fibers to become brittle over time and often causes the article to fail.
Accordingly, what is needed is an unmodified PVOH that may be thermoplastically formed into films and fibers which can then be used in the production of water-dispersible, flushable articles without the use of plasticizing agents. These fibers, films and fabrics could be used in products such as personal care products, diapers, feminine napkins, wipes, incontinence products, release liners, product packaging, etc., which contain the above-mentioned fibers, films and fabrics.